Lubricating oil



Patented 30, 1934 UNITED STATES LUBRICATING on.

' Bert H. Lincoln and Alfred Henriksen, Ponca City, Okla", assignors toContinental Oil Company, Ponca City, kla., a corporation of:

\ Delaware No Dre.

'5 Claims.

Our invention relates to lubricating oils and more particularly toimproved methods for the production of high quality lubricating oils andsuch products as new compositions of matter.

a It is well known that mineral lubricating oils are deficient inoiliness characteristics, which is the most important character of thelubricant when used under conditions of boundary lubrication, where theviscosity of the lubricant plays little or no part in lubrication.Boundary lubrication conditions are obtained when engines are operatingat heavy load, low' speeds or, if for any reason, the supply oflubricant is cut off or not suflicient. This last condition may existwhen for mechanical reasons the lubricant pump is not functioningproperly or when the lubricant feed line is clogged with foreign matter.

One object of our invention is to provide a lubricant of high oilinesscharacter, low coeflicient of friction, and one which will act as asafety factor in lubrication when abnormal conditions exist for onereason or another.

Another object of our invention is to provide a lubricant which willmaintain a very low coefficient of friction when diluted with lighthydrocarbons such as are obtained in an automobile crank case byincomplete combustion of the fuel.

A further object of our invention is to provide a lubricant havingpenetrative lubricity characteristics. It has been found that ourlubricant does not drain off the rubbing surfaces when idle, therebyproviding a lubricating film on the rubbing surfaces at all times andbeing of great value to-the life of the machine in cold weather startingwhen the lubricant is very viscous and sluggish.

It has been demonstrated a number of times that hydrocarbon lubricantsof the very best quality are not constant in coefficient of frictionwith slightly changing loads or speeds, and in some cases thecoefiicient of frictionvaries over rather v wide limits with somelubricants when all operating conditions are held constant.

Another object of our invention is to provide a lubricant which shows amore nearly constant coefflcient of friction, thereby insuring, smootherengine operation.

The method we have discovered and the lubricant prepared thereby foraccomplishing the above objects consists broadly of adding organic fattyacid esters to mineral hydrocarbon lubricants. We have found that acertain type organic ester gives a muchlmore constant coefficient offriction when added to a mineral lubricantlhan. is obtained by addingorganic fatty acids to the Application June 11, 1932 Serial No. 616,741

same lubricant. Another advantage of the organic esters over fatty acidsas addition products to lubricants is that organic esters may be usedwhen an acid free lubricant is required for one cause or another, suchas in the presence of easily corroded metals or alloys.

The theory of our invention is not fully understood, but we assume thatthe organic esters function due to their molecular polarity, whereas theorganic acids act entirely differently and. probably by soap formationon the metal surface with the free carboxyl group and residual metalaflinity. It has been proved by spectrum analyses and spectograms thatthe fatty acid carboxyl group forms a new compound (soap) with the metalsurface. The carboxyl is rooted in the metal and the long chainhydrocarbon radical standing on the carboxyl base perpendicular to themetal and parallel to each other. With the carboxyl acid afiinityneutralized by ester formation, the action of esters in reducingfriction must be different.

We are aware that fatty oils containing glycerides of fatty acids havebeen sulpho-chlorinated in order to improve the oil. An example of an 0oil thus sulpho-chlorinated is shown in U. S. patent to Sommer, 461,513,bearing date of October 20, 1891. It is to be observed, however, thatthe sulpho-chlorination of oils is not the equivalent of thechlorination of oils inasmuch as no 5 sulphuretting takes place in thechlorination of the oil. Furthermore, the glycerides are esters of thetri-atomic alcohol glycerol, while we employ esters of di-hydric ormono-hydric alcohols which are chlorinated.

In practicing our invention only small quantities of the various estersare added to hydrocarbon lubricants. The ester is well blended with thehydrocarbon and the mixture is ready for use. To prove the efficiencyand value of our invention, we determine the coefiicient of friction ofthe original hydrocarbon lubricant bytesting on the Herschel frictiontesting machine, which was developed by Dr. W. H. Herschel of the UnitedStates Bureau of Standards and is well known to the art. The coefficientof friction of the mixture of hydrocarbon oil and ester is thendetermined by the same machine. The following examples clearlydemonstrate the value and efliciency of this invention:

Example 1.--A very good quality, of 350 pale oil was selected as' thehydrocarbon lubricant for the test. Testing this product on the Herschelfriction machine gave a' coeflicientoffriction of 1 0.135, indicatingthat the original lubricant was of ver' high quality.

To t hydrocarbon lubricant 0.5% of commercial ethyl oleate was added andwell mixed. Testing this mixture on the Herschel machine gave acoefficient of friction of 0.065, or less than half the friction of theoriginal hydrocarbon lubricant. During the test the machine lubricatedwith the mixture gave very smooth operation. The indicating pointerreached the point 0.065 on the scale and was held at a constant pointthroughout the test. Hydrocarbon lubricants and hydrocarbon lubricantsblended with fatty acids have a tendency to fluctuate over rather widelimits when tested on this machine, their action being variable andjerky while the esters blended in accordance with our invention givevery smooth operation.

Example 2.Another sample of the hydrocarbon lubricant mentioned inExample 1 was blended with 0.5% of N-butyl oleate. This mixture gave acoefilcient of friction of 0.073, or a reduction in the coefficient offriction of about 46%. In this case as before, the operation of themachine was extremely smooth.

Example 3.-To another sample of the same hydrocarbon lubricant mentionedin Example 1, 0.5% ethyl palmitate was added. This mixture gave a verysmooth operation and a coefiicient of friction reading of 0.071% orabout &8% reduction.

but the above examples show Example 4.0.75% of ethyl stearate gave inthe same hydrocarbon lubricant a coefiicient of friction of 0.075 andvery smooth operation.

Example 5.-To another sample of the hydrocarbon lubricant mentioned inExample 1, 0.5% phenyl stearate was added. a This aromatic alcohol estergave a coemcient of friction reading of 0.075 and the operation wasextremely smooth.

Any number of other examples might be given that esters of fatty acidswith either aliphatic or aromatic alcohols are efficient in our process.It should be pointed out that the lower molecular weight fatty acidesters are not as efficient as the higher molecular weight fatty acidesters. For example, 0.50 ethyl butyrate in the same hydrocarbonlubricant as mentioned in Example 1 above gave a coefilcient of frictionreading of 0.080 and the operation was very irregular. 0.50 isopropyloxalate gave a very, high coemcient of friction, 0.130, and was veryirregular. 0.5% isopropyl acetate gave a reading of 0.085 but wasirregular in operation.

It is to be understood that the term esters" as used in the claims andin this specification is intended to cover all esters broadly, excludingthose low molecular weight acids which do not lower the coeflicient offriction. The commercial esters are satisfactory for this process; theimpurities present do not affect the efficiency. The esters may beprepared by any of the commercial esterification processes whereincommercial fatty acids and commercial alcohols are used as rawmaterials.

We have further found that original hydrocarbon lubricants andhydrocarbon lubricants blended with esters have low film strength andhave a tendency to break down and allow seizure of metals at relativelylow pressures. The film strength of a lubricant is of great importancewhen the lubricant is used under heavy loads and slow speeds. Byhalogenating the esters of this invention prior to blending withhydrocarbon lubricants the film strength is greatly improved,

The halogen may be added to the ester in any manner, the onlyrequirement being that the halogen is introduced in the molecule. Withesters of unsaturated fatty acids, the halogen may be added directlyuntil the unsaturated bonds are saturated with halogen. With furtherhalogenation, hydrogen is replaced by halogen by substitution. Saturatedmolecules are halogenated entirely by substitution. The halogen may beintroduced into the alcohol radical or the fatty acid radical prior toor after esterification.

As an example of one method of carrying out this phase of our invention,but not as a limitation thereto, the following demonstration is cited.

A sample of ethyl oleate was chlorinated until it was a liquid at roomtemperature. Excess chlorine and hydrogen chloride were removed bywarming and washing with solvents. The product thus prepared was addedto a sample of high quality lubricant and tested on the Timken machine,which is a machine for determining film strength of lubricants developedand manufactured by the Timken Roller Bearing Company and well known inthe art. A sample of the original hydrocarbon lubricant was also testedon the Timken machine. The original hydrocarbon lubricant broke down andallowed seizure of the metal rubbing surfaces when 18.2 pound weightshad been added, which is equivalent to'approximately 10,500 pounds persquare inch on the rubbing -surfaces. To another sample of this samehydrocarbon lubricant 0.5% of halogenated ethyl oleate was added. Thisproduct did not break down until 35.2 pound weights had been added,which represents a pressure of approximately 22,000 pounds per squareinch on the rubbing surfaces; thus by adding 0.5% of the product of thisinvention, the film strength of a lubricant can be practically doubled.

The degree of halogenation of the esters may be varied over wide'limitsdepending upon the ester used and the service in which the bed lubricantis to be used. In some cases small percentages of halogen in themolecule are sufficient; in others a large percentage of halogen isrequired.

When using poorer quality original hydrocarbon lubricants, largerquantities of ester and halogenated ester are required to obtain thedesired result. Quantities as high as 2% or more may be used. With anygiven hydrocarbon lubricant one skilled in the art of preparinglubricants can easily determine the percentage of ester or halogenatedester required to give the smooth operation, low coefiicient of frictionand/or high film strength. In most cases the quantity will vary between0.1% and 2%.

It will be understood that certain features and subcombinations are ofutility and may be employed without reference to other features andsub-combinations. This is contemplated by and is within the scope of ourclaims. It is further obvious that various changes may be made indetails within the scope of our claims without departing from the spiritof our invention. It

is, therefore, to be understood that our inven- 3. A lubricating 011comprising in combination a hydrocarbon oil and a small quantity of achlorinated ester of a fatty acid and a dihydric alcohol.

tion a hydrocarbon oil and a small quantity of chlorinated ethyl oleate.

4. A lubricating oil comprising in combina,

5. A lubricating 011 comprising in-combination a hydrocarbon oil and asmall quantity of chlorinated methyl stearate. a

BERT H. LINCOLN.

